Alcohol-modified polyepoxides, their preparation and their use in curable mixtures

ABSTRACT

This application discloses a synthetic resin based on alcohol-modified polyepoxides. The synthetic resin can be prepared by reacting a diepoxide, or a mixture of diepoxides, having an epoxide equivalent weight of less than about 500, with compounds with a hydroxyl group, which is reactive towards epoxide groups, in a molar ratio from about 2:1 to about 7:6 at temperatures from about 100° C. to about 180° C. in an organic solvent free of hydroxyl groups. The synthetic resin has terminal epoxide gorups and a mean molecular weight from about 400 to about 5000.

This is a division of application Ser. No. 711,997 filed Mar. 14, 1985,now U.S. Pat. No. 4,661,541.

The invention relates to novel polyepoxides which are prepared byreacting low-molecular polyepoxides with alcohols, and to their use incurable mixtures or their use as surface-coating resins, in particularas surface-coating resins for water-soluble or water-dispersible resins.

Polyepoxides in the form of polyglycidyl ethers of2,2-bis-(4-hydroxyphenyl)-propane and derivatives thereof have beenknown for a long time and thoroughly described as, for example, in"Epoxy Resins and Products", M. William Ranney, Noyes data Corporation,New Jersey 1977.

These polyglycidyl ethers have the following general structure ##STR1##where n=0 to about 12.

In addition, there are polyglycidyl ethers based onbis-(4-hydroxyphenyl)-methane and on bis-(4-hydroxycyclohexyl)-propane.Another form is based on the reaction product of phenol with heptanal(European patent application No. 43,612) to give1,1-bis-(4-hydroxyphenyl)-n-heptane.

Furthermore, polyepoxides are known which are based on polyglycidylesters, polyglycidyl-hydantoins or diepoxy compounds.

In many fields of application, the attainable properties of the epoxideresins, built up from the structures described above, are notsatisfactory. Thus, for example, epoxide resins have a relatively lowcompatibility with aliphatic hydrocarbons. Another area where the knownepoxide resins need to be improved, concerns the elasticity. It is alsoknown that there are problems with the ability of the epoxide resins tobe overpainted or adhesively bonded, and with their surface resistivity.

It is the object of this invention to provide novel, improved epoxideresins. The possibility of modifying epoxide resins which, surprisingly,has been found, makes it possible to build up epoxide resins in acontrolled manner by the same process for the most diverse purposes.

These novel polyepoxides modified by side chains are the reactionproduct of low-molecular polyepoxides, in particular bisglycidyl ethers,with low-molecular monohydric alcohols which, if desired, also containone or more further, sterically strongly hindered hydroxyl groups, sothat a linear chain build-up with the epoxide resins is impossible, togive higher-molecular polyepoxides which, if desired, are elasticized ina further reaction step.

The invention therefore relates to a synthetic resin based onalcohol-modified polyepoxides, which is obtainable by reacting

(A) a diepoxide, or a mixture of diepoxides, having an epoxideequivalent weight of less than 500, with

(B) compounds with a hydroxyl group, which is reactive towards epoxidegroups, in a molar ratio of 2:1 to 7:6, preferably 2:1 to 5:4, andparticularly preferably 2:1 to 4:3, at temperatures from 100° to 180° C.in an organic solvent free of hydroxyl groups, in the presence orabsence of a tertiary amine as a catalyst, the synthetic resin havingterminal epoxide groups and a mean molecular weight from 400 to 5000.

This polyepoxide which has been modified by side chains and, if desired,elasticized by the component (C), can be further reacted with amines foruse in aqueous systems.

In the reaction of the polyepoxide (A) with the component (B), thefollowing reaction steps take place.

1st part step: opening of an oxirane ring by the monohydric alcohol togive an intermediate ##STR2## followed by

2nd part step: opening of a further oxirane ring by the hydroxyl groupformed in the 1st part step ##STR3## where R'=organic radicals of thealcohol.

R represents the radicals of the following or similar structures

R=X or --O--X--O--

X=alkylene or cycloalkylene

for example ##STR4##

Any monohydric alcohols are in principle suitable for the reaction.

Suitable monohydric alcohols are methanol, ethanol, propanol,isopropanol, butanol, isobutanol, amyl alcohol, isoamyl alcohol,2-ethylbutanol, 2-ethylhexanol, isononyl alcohol, isodecyl alcohol,isotridecyl alcohol, isohexadecyl alcohol, isooctadecyl alcohol and alsoneopentyl alcohol, 3,7-dimethyl-octan-3-ol, 3-cyclohexylpropanol and2,4-dimethylpentan-3-ol.

Unsaturated monohydric alcohols, such as but-1-en-3-ol,2-methylbut-3-en-2-ol and 3-methylpent-1-en-3-ol, are likewise suitable.

Suitable araliphatic alcohols are benzyl alcohol, 4-methylbenzylalcohol, phenylethyl alcohol and 2-phenylpropan-1-ol.

Furthermore, cycloaliphatic alcohols, such as cyclohexanol and4-tertiary-butylcyclohexanol, are suitable. suitable hydroxy ethers arethe methyl, ethyl and butyl ethers of ethylene glycol, diethyleneglycol, triethylene glycol and polyethylene glycol as well asmethoxybutanol, methoxypropanol, phenylglycol, phenyldiglycol,hexylglycol and hexyldiglycol.

In addition, the following alcohols can be used: ethylthioethanol andmonoalcoholic prepolymers, for example the reaction product of one ofthe abovementioned monoalcohols with lactones, such as ε-caprolactone.

All low-molecular polyols which contain only one reactive hydroxyl groupand one or more further, sterically strongly hindered hydroxyl groups,so that a linear chain build-up with the epoxide resins is impossible,are also suitable for the reaction.

Typical examples of polyols of this nature are:2,2,4-trimethylpentane-1,3-diol or similar diols which can be preparedfrom formaldehyde and suitable ketones with subsequent reduction.Furthermore, 2-methylpropane-1,2-diol and similar diols as well as diolssuch as 2-methylpent-3-yne-2,5-diol are suitable.

When used in cathodic electrocoatings, these alcohols lead toparticularly thick coating films.

The polyfunctional alcohols, polycarboxylic acids, polyamines orpolysulfides, suitable as the component C, have a molecular weight from300 to 3500, preferably from 350 to 1000.

The polyols suitable for the invention include diols, triols and higherpolymeric polyols, such as polyester-polyols and polyether-polyols.

Polyalkylene-ether-polyols suitable for component C are of the generalformula: ##STR5## where R=hydrogen or a lower alkyl radical, which maycarry various substituents, n=2 to 6 and m=3 to 50 or even higher.Poly-(oxytetramethylene)-glycols and poly-(oxyethylene)-glycols areexamples.

The preferred polyalkylene-ether-polyols arepoly(oxytetramethylene)-glycols having a molecular weight in the rangefrom 350 to 1000.

The polyester-polyols can also be used as a polymeric polyol component(component C) in the invention. The polyester-polyols can be prepared bypoly-esterification of organic polycarboxylic acids or their anhydrideswith organic polyols which contain primary hydroxyl groups. Usually, thepolycarboxylic acids and the polyols are aliphatic or aromaticdicarboxylic acids and diols.

The diols used for the preparation of the polyesters include alkyleneglycols, such as ethylene glycol, butylene glycol and neopentyl glycol,and other glycols such as cyclohexanedimethanol.

The acid component of the polyester consists especially of low-molecularcarboxylic acids, or their anhydrides, of 2 to 18 carbons in themolecule. Examples of suitable acids are phthalic acid, isophthalicacid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalicacid, adipic acid, azelaic acid, sebacic acid, maleic acid and glutaricacid. In place of these acids, their anhydrides can also be used,provided that these exist.

Moreover, polyester-polyols derived from lactones can be used as thecomponent (C) in the invention. These products are obtained by reactingε-caprolactone with a polyol. Such products are described in U.S. Pat.No. 3,169,945.

The polylactone-polyols obtained by this reaction are distinguished bythe presence of a terminal hydroxyl group and by recurring polyestermoieties derived from the lactone. These recurring molecule moieties canbe of the formula ##STR6## where n is at least 4, preferably 4 to 6, andthe substituent is hydrogen, alkyl, cycloalkyl or alkoxy.

In a further advantageous embodiment of the invention, long-chaindicarboxylic acids are used. Examples of these are dimeric fatty acids,such as dimeric linoleic acid.

Suitable polyamines for elasticization can be prepared, for example, byreaction of primary diamines and monoepoxides. The secondary,substituted diamines formed modify the epoxide resins according to theinvention in a suitable manner.

The polyfunctional SH compounds (component C) can be reaction productsof organic dihalides with sodium polysulfide. Further SH compounds are,for example, reaction products of linear polyesters, polyethers orpolyurethanes, containing hydroxyl groups, with mercaptocarboxylic acidssuch as mercaptoacetic acid, 2-mercaptopropionic acid,3-mercaptopropionic acid, mercaptobutyric acid and the like.

Elasticizing polyphenols suitable for component (C) are of the generalformula explained above ##STR7##

This component (C) can be advantageously prepared, for example, in thefollowing manner. One mole of a higher-molecular diol, for example of apolyester-diol, a polycaprolactone-diol, a polyether-diol, apolycarbonate-diol or the like, is esterified with two moles of ahydroxyphenylcarboxylic acid or reacted with two moles of ahydroxyphenylcarboxylic acid ester. Suitable hydroxycarboxylic acids aren-hydroxybenzoic acid, n-hydroxyphenylacetic acid and3-(4-hydroxyphenyl)-propionic acid, or esters thereof. If thehydroxylphenyl group is attached by transesterification, basictransesterification can also be carried out and the alkali metalphenolates of the corresponding hydroxyphenylcarboxylic acid esters canbe used for this purpose. After the end of the reaction, the productmust be processed under acidic conditions in order to obtain the desiredpolyphenol.

For direct esterification, N-(4-hydroxyphenyl)glycine can, for example,also be used. In a further variant, any acidic polyesters can be reactedwith n-hydroxyaniline to give the desired polyphenols.

In another advantageous embodiment, polyetherdiamines or similarpolyamines are reacted with, for example,4-hydroxy-3-methoxybenzaldehyde to give the polyphenols.

The starting polyepoxide is reacted with the low-molecular monoalcohol,which may also contain one or more further, sterically strongly hinderedhydroxyl groups, in such a stoichiometric ratio that higher-molecularepoxide resins are obtained. The epoxide resins, which still containintact oxirane groups, can then be mixed in the usual manner with curingagents, if appropriate from a solution.

Virtually any compounds which are at least bifunctional and react withoxirane groups can be used as curing agents, for example polyalcohols,polyphenols, polycarboxylic acids and their anhydrides, and amides,amines, polyisocyanates, phenoplasts, and the like. These mixtures canbe used for cold-curing and hot-curing coatings, for filled and unfilledcasting resins, for example for potting electronic components and theimpregnation of windings. Furthermore, these mixtures are suitable asbinders for fiber-reinforced resins and for high-grade adhesives.

For the use of the epoxide resins according to the invention in aqueoussystems, it is necessary to introduce ionic groups in the resins. Thus,acid groups can be introduced by suitable methods and, afterneutralization with amines, these give a water-soluble resin.

For the electrocoating of metallic substrates, which has in the meantimefound wider acceptance, cathodic electrocoating is nowadayspreferentially used. In this case, the resin carries positive charges.

These can be generated, for example, by reacting the epoxide resins withamines and subsequent neutralization with carboxylic acids.

The amine used for this reaction with the epoxide compound can beprimary or secondary, secondary amines being particularly suitable.Primary and secondary amines can be added directly to the epoxide ring.Tertiary amines can be incorporated in the molecule only via a furtherfunctional group. Preferably, the amine should be a water-solublecompound. Examples of such amines are mono- and di-alkylamines, such asmethylamine, ethylamine, propylamine, butylamine, dimethylamine,diethylamine, dipropylamine, methylbutylamine and the like.Alkanolamines, for example methylethanolamine, diethanolamine and thelike, are likewise suitable. In addition, dialkylaminoalkylamines, forexample dimethylaminoethylamine, diethylaminopropylamine and the like,are suitable.

In most cases, low-molecular amines are used, but it is also possible toemploy higher-molecular monoamines.

Polyamines having primary and secondary amino groups can be reacted inthe form of their ketimines with the epoxide groups. The ketimines areprepared from the polyamines in a conventional manner.

The amines can also contain further groups, but these should notinterfere with the reaction of the amine with the epoxide group, norlead to gelling of the reaction mixture.

The reaction of the amine with the compound containing epoxy groupsfrequently starts even during the mixing of these materials. In somecases, however, heating to moderately elevated temperatures may bedesirable, for example to 50° to 150° C., but reactions are alsopossible at lower and higher temperatures. Frequently, it isadvantageous to raise the temperature at least slightly for a sufficientperiod towards the end of the reaction, in order to ensure completeconversion.

For the reaction with the epoxy-containing compound, sufficient amineshould be so used that the resin assumes a cationic character, ie. thatit migrates to the cathode under the reaction of a voltage in thecoating bath, provided that it has been rendered soluble by addition ofan acid. Virtually all the epoxy groups of the resin can be reacted withan amine. It is also possible, however, to leave excess epoxy groups inthe resin, and these hydrolyze on contact with water, hydroxyl groupsbeing formed.

A further possibility for obtaining the requisite dispersibility inwater is the use of Mannich bases, ie. reaction products of suitablephenols, carrying groups suitable for a reaction with an epoxide ring,with formaldehyde and a secondary amine. In this way, the binder becomesself-crosslinkable at the same time.

Acids which are suitable for neutralizing the amines and which can beused in the invention, include boric acid or other acids having adissociation constant constant greater than that of boric acid,preferably organic acids having a dissociation constant greater thanabout 1×10⁻⁵. The preferred acid is acetic acid. Examples of other acidsare formic acid, lactic acid, propionic acid, butyric acid, hydrochloricacid, phosphoric acid, sulfuric acid and carbonic acid.

The requisite charges can also be generated by reacting the oxiranegroups with salts of an amine or of a sulfide/acid mixture orphosphine/acid mixture. The salt of a tertiary amine can be used as thesalt of an amine.

The amine moiety of the amine/acid salt is an amine which can beunsubstituted or substituted, as in the case of hydroxylamines, andthese substituents should not interfere with the reaction of theamine/acid salt with the polyepoxide, and the reaction mixture shouldnot gel. Preferred amines are tertiary amines, such asdimethylethanolamine, triethylamine, trimethylamine, triisopropylamineand the like. Examples of other suitable amines are given in U.S. Pat.No. 3,839,252 in column 5, line 3, to column 7, line 42.

The amine/acid salt mixture is obtained in the conventional manner byreacting the amine with the acid. Amine/acid mixtures can also be used,even though these react as a rule with formation of the salt of theacid.

The temperature for the reaction of the amine/acid salts with thepolyepoxides can be varied within the range from the lowest temperatureat which the reaction preoceeds at a significant rate, for example roomtemperature or as a rule slightly above room temperature, up to amaximum temperature from about 100° to about 110° C. A solvent is notnecessary in the reaction, even though a solvent is frequently added inorder to facilitate control of the reaction. Suitable solvents arearomatic hydrocarbons or monoalkyl ethers of ethylene glycol.

The ratio of the amine/acid salt and the epoxy compound can vary, andthe optimum ratios depend on the particular starting materials. Ingeneral, about 1 to about 50 parts by weight of salt per 100 parts byweight of polyepoxide can be used. In general, the ratio is selected asa function of the nitrogen content derived from the quaternizing agent;typically this amounts to about 0.05 to about 16%, based on the totalweight of the amine salt and the polyepoxide.

The resins can contain all the nitrogen in the form of chemically boundquaternary ammonium salt groups, even though less than 100% of thenitrogen is present in some cases in the form of quaternary ammoniumsalt groups. This is the case, for example, when primary and secondaryamines are used for the preparation of the resins with ammonium saltgroups. Such resins contain as a rule secondary and tertiary amine saltgroups.

Resins with phosphonium groups can be prepared by reacting the epoxidecompounds defined above with a phosphine in the presence of an acid, aresin having a group of a quaternary phosphonium base being formed.

Any phosphine which does not contain interfering groups can be used.Examples of such phosphines are aliphatic, aromatic or alicyclicphosphines, and the following phosphines may be mentioned as specificexamples:

Lower trialkylphosphines, such as trimethylphosphine, triethylphosphine,tripropylphospine, tributylphosphine, mixed lower alkylphenylphosphines,such as phenyldimethylphosphine, phenyldiethylphosphine,phenyldipropylphospine, diphenylmethylphosphine, diphenylethylphosphineand diphenylpropylphosphine, triphenylphosphine, alicyclic phosphines,such as tetramethylene-ethylphosphine, and the like.

Any acid forming a quaternary phosphonium salt can be used. Preferably,however, the acid is an organic carboxylic acid. Examples of suitableacids are boric acid, lactic acid, formic acid, acetic acid, propionicacid, butyric acid, hydrochloric acid, phosphoric acid and sulfuricacid.

Preferably, the acid should have a dissociation constant greater thanabout 10⁻⁵.

The ratio of phosphine and acid is not particularly critical. Since oneequivalent of acid is required for forming one mole of a phosphoniumgroup, at least about one equivalent of acid is preferably used for eachmole of the desired conversion of phosphine into phosphonium.

The phosphine/acid mixture and the epoxide compound are reacted bymixing the components, sometimes with heating to moderately elevatedtemperatures. The reaction temperature is not particularly critical, andis selected as a function of the starting materials and their reactionrates. Frequently, the reaction proceeds at a satisfactory rate at roomtemperature or at temperatures raised up to 70° C. In some cases, it isadvisable to use higher temperatures, such as about 110° C. or higher. Asolvent is not necessary, even though it can frequently be used forimproving control of the reaction. Examples of suitable solvents arearomatic hydrocarbons, monoalkyl ethers of ethylene glycol and aliphaticalcohols. The quantitative proportions of the phosphine and the epoxidecompound can be varied, and the optimum proportions depend on theparticular starting materials. Usually, however, about 1 to about 50parts by weight of phosphine are used per 100 parts by weight of theepoxide compound. The quantitative proportions are frequently stated byreference to the proportion of phosphine and, typically, about 0.1 toabout 35% by weight of phosphine, based on the total weight of phosphineand epoxide compound, are used.

Resins with sulfonium groups can be prepared by reacting the epoxycompounds defined above with a sulfide in the presence of an acid, aresin having groups of a tertiary sulfonium base being formed.

Any sulfides which react with epoxy groups and do not contain groupsinterfering with the reaction can be used. The sulfide can be analiphatic, mixed aliphatic-aromatic, aralkylic or cyclic sulfide.Examples of such sulfides are dialkyl sulfides, such as diethyl sulfide,dipropyl sulfide, dibutyl sulfide or dihexyl sulfide, or alkyl phenylsulfides, such as diphenyl sulfide and ethyl phenyl sulfide, alicyclicsulfides, such as tetramethylene sulfide and pentamethylene sulfide,hydroxyalkyl sulfides, such as thiodiethanol, thiodipropanol andthiodibutanol, and the like.

Any acid which forms a tertiary sulfonium salt can be used. Preferably,however, the acid is an organic carboxylic acid. Examples of suitableacids are boric acid, formic acid, lactic acid, acetic acid, propionicacid, butyric acid, hydrochloric acid, phosphoric acid and sulfuricacid. Preferably, the acid has a dissociation constant greater thanabout 1×10⁻⁵.

The ratio of sulfide and acid is not particularly critical. Since oneequivalent of acid is used for the formation of one mole of a sulfoniumgroup, preferably at least one equivalent of acid is used for everydesired mole to be converted from sulfide to sulfonium.

The sulfide/acid mixture and the epoxide compound are reacted by mixingthe components and heating them as a rule to moderately elevatedtemperatures, such as 70° to 110° C. A solvent is not necessary,although frequently a solvent is used in order to achieve better controlof the reaction. Suitable solvents are aromatic hydrocarbons, monoalkylethers of ethylene glycol and aliphatic alcohols. The quantitativeproportions of the sulfide and the epoxide compound can be varied, andthe optimum ratios of the two components depend on the particularstarting materials. Usually, however, about 1 to 50 parts by weight ofsulfide are used per 100 parts by weight of epoxy compound. Thequantitative ratios are frequently related to the sulfur content whichtypically is about 0.1 to 35%, based on the total weight of the sulfideand epoxy compound.

In order to obtain highly resistant coatings when the binders accordingto the invention are used, it is advantageous to add to theelectrocoating a crosslinking agent which effects crosslinking of thebinder at elevated temperatures or to modify the binder in such a waythat it contains reactive groups which effect self-crosslinking atelevated temperatures. A self-crosslinking system can advantageously beobtained by reacting the binder with a partially blocked polyisocyanatewhich has one free isocyanate group per molecule on average and theblocked isocyanate groups of which are stable at room temperature andare unblocked at elevated temperatures and react with the hydroxylgroups formed by the opening of the epoxide rings, a urethane beingformed.

Frequently applied methods for the crosslinking of binders have beenpublished, for example, in German Offenlegungsschriften Nos. 2,057,799and 2,752,256, and in European Patent Applications Nos. 12,463 and4,090. However, this listing does not restrict the type of crosslinkingagents.

If crosslinking agents are used, they amount as a rule to about 5 toabout 60% by weight of the binder. About 20 to about 40% by weight ofbinder are preferred.

Blocked polyisocyanates are preferably used as the crosslinking agents.Any polyisocyanates can be used in the invention, in which theisocyanate groups have been reacted with a compound in such a way thatthe blocked polyisocyanate formed is resistant to hydroxyl groups atroom temperature but reacts at elevated temperatures, as a rule in therange from about 90° to about 300° C. Isocyanates of about 3 to about 36carbons, in particular about 8 to about 15 carbons, are preferred.

The organic polyisocyanates to be used as cross-linking agents in theinvention can also be prepolymers which are derived, for example, from apolyol including a polyether-polyol or a polyester-polyol. As is known,polyols are reacted for this purpose with an excess of polyisocyanates,so that prepolymers with terminal isocyanate groups are formed.

Any suitable aliphatic, cycloaliphatic or aromatic monohydric alcoholscan be used for blocking the polyisocyanates. Small proportions ofhigher-molecular monohydric alcohols of relatively low volatility canalso be used in addition, if desired, these alcohols acting asplasticizers in the coatings, after they have been split off.

Other suitable blocking agents are hydroxyamines, such as ethanolamine,and oximes, such as methyl ethyl ketone oxime, acetone oxime andcyclohexanone oxime.

The blocked polyisocyanates are prepared by reacting a sufficientquantity of an alcohol with the organic polyisocyanate in such a waythat free isocyanate groups are no longer present. The reaction of theorganic polyisocyanate with the blocking agent is exothermic. For thisreason, the polyisocyanate and the blocking agent are preferably mixedat a temperature which does not exceed 80° C., and, in particular, isbelow 50° C., in order to counteract the exothermic effect.

The polyisocyanates and blocking agents mentioned can, in appropriatequantitative ratios, also be used for the preparation of the partiallyblocked polyisocyanates described above.

The onium-modified binders according to the invention are also suitablein a special manner for the preparation of pigment pastes, ie. thebinder is used as a grinding resin.

When the resin according to the invention is used as a grinding resinfor the preparation of a pigment paste, the quantitative ratios of theepoxy-containing organic material and of the organic tertiary amine,which are reacted with one another, are preferably selected such thatthe carrier resin contains 0.8 to 2.0 nitrogen atoms per molecule. Lowerquantities of quaternary nitrogen can lead to poor wettability of thepigment, whereas larger quantities have the consequence that the resinsare excessively soluble in water.

Pigment pastes according to the invention are prepared by comminuting ordispersing a pigment in the grinding resin in the well-known manner. Thepigment paste contains the grinding resin and at least one pigment asthe essential constituents.

In addition, however, the pigment composition can also contain otherconventional additives, such as plasticizers, wetting agents,surfactants or antifoams.

Grinding of the pigments is carried out as a rule in ball mills, sandmills, Cowles mills and continuous grinding equipment, until the pigmenthas been comminuted to the desired particle size and, preferably, hasbeen wetted by the resin or dispersed therein. After comminution, theparticle size of the pigment should be in the range of 10 micron orsmaller. In general, the comminution is taken to a Hegman fineness ofabout 6 to 8.

Preferably, grinding is carried out in an aqueous dispersion of thegrinding resin. The quantity of water present in the mass to be groundshould be sufficient to form a continuous aqueous phase.

The well-known pigments can be used as the pigment in the invention. Ingeneral, titanium dioxide is the only or the main white pigment.However, other white pigments or extenders, such as antimony oxide, zincoxide, basic lead carbonate, basic lead sulfate, barium carbonate,porcelain, clay, calcium carbonate, aluminum silicate, silica, magnesiumcarbonate and magnesium silicate, can also be used. Examples of coloredpigments which can be used are cadmium yellow, cadmium red, carbonblack, phthalocyanine blue, chromium yellow, toluidine red and hydratediron oxide. For further general references to the comminution ofpigments and the formulation of paints, the following books are quoted:

D. H. Parker, Principles of Surface Coating Technology, IntersciencePublishers, New York (1965)

R. L. Yates, Elektropainting, Robert Draper Ltd., Teddington England(1966)

H. F. Payne, Organic Coating Technology, volume 2, Wiley and Sons, NewYork (1961).

The invention also relates to a process for preparing binders, whichcomprises reacting

(A) a diepoxide, or a mixture of diepoxides, having an epoxideequivalent weight of less than 500, at temperatures from 100° to 180° C.in a solvent free of hydroxyl groups, in the presence or absence of atertiary amine as a catalyst with

(B) compounds with a hydroxyl group, which is reactive towards epoxidegroups, in a molar ratio of 2:1 to 7:6, preferably 2:1 to 5:4, andparticularly preferably 2:1 to 4:3, to give a synthetic resin havingterminal epoxide groups and a mean molecular weight from 400 to 5000.

This side chain-modified polyepoxide, which may have been elasticized bycomponent (C), can be further reacted with amines for use in aqueoussystems.

Advantageous embodiments of the process according to the invention canbe seen from claims 8 to 12.

The process is carried out as follows: component A and component B aremixed and, in the presence or absence of catalysts, for example tertiaryamines, are completely converted at temperatures from 100° to 140° C.,preferably 115° to 135° C. The reaction can be monitored by means of theepoxide equivalent weight. This reaction product of components A and Bcan be further modified with component C at temperatures from 100° to170° C. This reaction can also be followed by means of the epoxideequivalent weight. The reaction product thus obtained still containsfree epoxide groups.

For this reaction step, the same catalysts as in the reaction ofcomponents A and B can be used. The reaction product thus obtained can,if desired, be reacted with amines at temperatures from 90° to 120° C.,so that a binder containing basic amino groups is formed. The basicreaction product can be wholly or partially protonized by the additionof acids and can then be dispersed in water. The cross-linking agent canbe admixed to the binder before the dispersion in water or, depending onthe reactivity, it can be introduced during the preparation of thebinder. In the case of partially blocked polyisocyanates, these arereacted with the binder at temperatures from 80° to 150° C., preferably100° to 130° C. The binders obtained are stable dispersions which areeasy to handle. In some cases, it can also be appropriate to dissolvethe binders in suitable organic solvents before preparing thedispersion. Examples of suitable solvents are glycol ethers,ethylglycol, butylglycol, ketones such as diethyl ketone, methyl ethylketone and methyl isobutyl ketone, and others.

The invention also relates to the use of the binders for electrocoatingbaths.

The electrocoating baths can contain conventional pigments. Frequently,a dispersant or a surfactant is added to the pigments. The pigment andthe surfactant, if used, are ground together in a part of the binder, orby themselves, in order to prepare a paste which is extended by theremaining binder for preparing the coating composition.

In some cases, it is advantageous to add to the electrocoating bath anon-ionic modifier or solvent, in order to improve the dispersibility,the viscosity and/or the film quality. Examples of such materials arealiphatic, naphthenic and aromatic hydrocarbons or mixtures thereof,mono- and di-alkyl ethers of glycols, Siberian pine needle oil and othersolvents which are compatible with the resin system. The modifierpreferred at present is propylene glycol phenyl ether.

Furthermore, other additives such as antioxidants can be added to theelectrocoating bath. Examples are ortho-amylphenol or cresol. Theaddition of such antioxidants is particularly desirable whenever thedeposition baths are exposed to atmospheric oxygen at elevatedtemperatures for prolonged periods with stirring.

Other additives which the bath may contain are wetting agents, such aspetroleum-sulfonates, sulfated fatty amines or amides thereof, esters ofsodium isethionates, alkylphenoxypolyethylene alcohols or phosphateesters, including ethoxylated alkylphenol phosphates. Other groups ofpossible additives are antifoams and suspending agents. Ordinary tapwater can be used for formulating the deposition bath. However, sincesuch water contains relatively high proportions of salts, undesiredchanges can therefore occur during the electrodeposition. Deionizedwater is therefore generally preferred. The above list of possibleadditives is not complete, since many other additives which do notinterfere with the electrodeposition can be used.

The invention also relates to a process for electrophoretically coatingan electrically conductive substrate, connected as the cathode, from anaqueous bath based on a cationic binder at least partially neutralizedwith acids, the binders having been rendered self-crosslinkable by areaction or the bath containing an additional crosslinking agent,wherein the binders are reaction products of

(A) a diepoxide, or a mixture of diepoxides, having an epoxideequivalent weight of less than 500, with

(B) compounds with a hydroxyl group, which is reactive towards epoxidegroups, in a molar ratio of 2:1 to 7:6, preferably 2:1 to 5:4, andparticularly preferably 2:1 to 4:3, at temperatures from 100° to 180° C.in an organic solvent free of hydroxyl groups, in the presence orabsence of a tertiary amine as a catalyst, the synthetic resin havingterminal epoxide groups and a mean molecular weight from 400 to 5000.

This side chain-modified polyepoxide, which may have been elasticized bycomponent (C), is further reacted with amines.

The substrate in the electrodeposition can be any electricallyconductive substrate. Usually, these are metal substrates, for exampleiron, steel, copper, zinc, brass, tin, nickel, chromium and aluminum aswell as other metals, pretreated metals, and also phosphatized orchromized metals. Impregnated paper and other conductive substrates canalso be used.

In the cationic deposition, the articles to be coated are immersed in anaqueous dispersion of the solubilized film-forming cationic binder. Anelectric voltage is applied between the article to be coated, whichfunctions as the cathode, and an anode, and the cationic binder isdeposited on the cathode by the electric current. The article is thentaken out of the bath and as a rule rinsed. The coating is then cured inthe conventional manner by heating.

The invention is explained in more detail in the examples which follow.All the data on parts and percentages are by weight, unless explicitlystated otherwise.

PREPARATION OF CROSSLINKING AGENT I

According to German Offenlegungsschrift No. 2,701,002, Example 1, ablocked isocyanate crosslinking agent (polyurethane crosslinking agent)is prepared by adding 218 parts of 2-ethylhexanol slowly to 291 parts ofan 80/20 isomer mixture of 2,4-/2,6-toluylene diisocyanate with stirringand under a nitrogen atmosphere, the reaction temperature being keptbelow 38° C. by external cooling. The batch is maintained for a furtherhalf an hour at 38° C. and is then heated to 60° C., whereupon 75 partsof trimethylolpropane and then 0.08 part of dibutyl-tin dilaurate as acatalyst are added. After an exothermic reaction at the start, the batchis maintained for 1.5 hours at 121° C., until substantially all theisocyanate groups have been consumed, which is detectable in theinfrared spectrum. The batch is then diluted with 249 parts of ethyleneglycol monoethyl ether.

PREPARATION OF CROSSLINKING AGENT II

A polyester crosslinking agent is prepared according to European Pat.No. 0,040,867, Example 2(d): 192 parts of trimellitic anhydride and 500parts of Versatic acid glycidyl ester having an epoxide equivalentweight of 250 are mixed and heated to 100° C., with stirring. Anexothermic reaction takes place, and the temperature rises to 190° C.After cooling to 140° C., 2 parts of benzyldimethylamine are added. Themixture is maintained at 140° C. for 3 hours. This gives a viscous,clear product, which is additionally diluted with 295 parts of ethyleneglycol monobutyl ether.

PREPARATION OF CROSSLINKING AGENT III

A crosslinking agent which carries β-alkoxyalkyl ester groups active forcrosslinking is prepared as follows:

In a reaction vessel which can be heated by a heat transfer oil and isfitted with a water separator, reflux condenser and an interposedRaschig column, 1000 g of succinic anhydride (10 mol) are added to 1462g of hexylglycol (10 mol), with stirring and under an inert gas supply.The reaction mixture is heated to 120° C., the temperature being brieflyraised to 130° C. by the exothermic heat of reaction. The temperature ismaintained, until the acid number is 230 mg of KOH/g.

400 g of xylene, 5 g of N-cetyl-N,N,N-trimethylammonium bromide and 940g of a bisphenol A epoxide resin having an epoxide equivalent weight of188 (2.5 mol) are then added. Within 1 hour, the temperature is raisedagain to 130° C. and maintained there until the epoxide number hasfallen to zero. After the addition of 2 g of p-toluene sulfonic acidsolution (25% in n-propanol), the temperature is raised to 200° C. inthe course of 4 hours, while the water of reaction formed iscontinuously removed from the system. The temperature is raised furtherto 220° C. and maintained there until approximately 90 g of water havebeen separated off and the acid number has fallen to less than 2 mg ofKOH/g of solid resin. The mixture is then cooled and discharged withoutdilution.

Solids content: 95.2% by weight (measured after heating to 130° C. for 1hour)

Acid number: 1.1 mg of KOH/g of solid resin

Viscosity: 480 mPas (measured at 25° C. after dilution with methylisobutyl ketone to 70% by weight)

PREPARATION OF CROSSLINKING AGENT IV

2340 g of the glycidyl ester of 2-methyl-2-ethyl-heptanoic acid areheated with 2073 g of trimellitic anhydride to 130° C. in a reactionvessel. While the mixture is being heated up, the strongly exothermicreaction starts. The reaction mixture is kept at 150° C. by externalcooling, until an acid number of 183 has been reached. The mixture isthen cooled to 90° C. and 1450 g of MIBK (methyl isobutyl ketone) areadded. Subsequently, 835 g of propylene oxide are slowly added dropwise.At an acid number of 2, the reaction is stopped. The solids content ofthe resin solution is adjusted to 70% with more MIBK.

PREPARATION OF ELASTICIZED POLYPHENOL I

500 g of a polycaprolactone-diol (OH number 210.9) and 286 g of methylp-hydroxybenzoate are introduced into a suitable reaction vessel withfacilities for introducing blanketing gas. The mixture is heated to 140°C. and homogenized. 3.9 g of tin octoate are then added and the mixtureis heated to 180° C., the elimination of methanol starting. After theend of the elimination, the mixture is stirred for a further hour at180° C. and the product is then cooled.

PREPARATION OF ELASTICIZED POLYPHENOL II

The procedure is as in the preparation of polyphenol I, but 695 g of apolytetrahydrofuran-diol are used instead of the polycaprolactone-diol.

PREPARATION OF ELACTICIZED POLYPHENOL III

550 g of adipic acid, 262 g of neopentyl glycol, 49 g of xylene and 0.8g of dimbutyl-tin oxide are introduced into a suitable reactor and themixture is heated. At 132° C., water begins to separate out. Thetemperature is raised slowly to 186° C. and maintained until theappropriate quantity of water (90 g) has been removed from the system.The mixture is then cooled to 100°, and 274 g of p-aminophenol areadded. The temperature is then raised again, and renewed elimination ofwater starts at 162° C. The temperature is slowly raised to 185° C. andkept constant, until 45 g of water have been eliminated. Subsequently,the xylene is distilled off. For introducing the elasticized binder intothe resins, the polyphenol is preheated to 100° C.

PREPARATION OF AN AMINE SALT

528 parts of dimethylethanolamine are introduced into a suitablereaction vessel. 712 parts of 88% lactic acid are then added withvigorous stirring, followed by 560 parts of deionized water. Due to theheat of neutralization, the temperature rises. After the end of theaddition, it is held at 85° C. for a further 3 hours. The mixture isthen cooled, and the amine salt solution is filtered.

PREPARATION OF A SULFIDE/ACID SALT MIXTURE

The procedure followed is as in the preparation of the amine salt, butthe following components are used:

617 parts of bis-(2-hydroxyethyl)sulfide

662 parts of 88% lactic acid

521 parts of deionized water

PREPARATION OF A SEMI-MASKED ISOCYANATE

107 parts of 2,4-toluylene diisocyanate and 11 parts of methyl isobutylketone are introduced into a dry reactor under a blanketing gas. 82parts of 2-ethylhexanol are added dropwise to the mixture. During thisaddition, the temperature must not exceed 65° C. After the end of theaddition, the temperature is maintained for a further 2 hours and themixture is then cooled to room temperature. Until it is used further,the product must be kept dry and under a blanketing gas.

PREPARATION OF BINDER I

1560 parts of a liquid epoxide resin based on bisphenol A and having anepoxide equivalent weight of 188 are introduced, together with 242 g ofhexylglycol, 41 parts of xylene and 7 parts of dimethylbenzylamine, intoa reaction vessel fitted with a stirrer, reflux condenser, internalthermometer and nitrogen inlet. The reaction mixture is heated to 130°C. and maintained at this temperature until the epoxide equivalentweight has reached a value of 350. The reaction mixture is then heatedto 160° C. and 378 parts of bisphenol A are added at the same time.After a reaction period of 20 minutes at this temperature, the mixtureis cooled to 100° C. and diluted with 430 parts of xylene. At this time,the epoxide equivalent weight is 1350. 122 parts of diethanolamine and83 parts of a reaction product from equimolar amounts ofN,N-diethylaminoethylamine and butylene oxide are then added. Thereaction is continued for 2 hours at 105° C., before the mixture isdiluted with 120 parts of hexylglycol and discharged. This gives a clearresin solution having a solids content of 80% and an MEQ-base value of0.85 milliequivalent/g of solid resin.

The binder is then converted into aqueous dispersions. The componentsgiven in the Table which follows are mixed, and deionized water (item 1)is added. After homogenizing for 20 minutes, the mixture is dilutedfurther with deionized water (item 2). The dispersions are thensubjected to a short vacuum distillation, the organic phase beingseparated off from the distillate.

    ______________________________________                                                   Dispersion                                                                             Dispersion Dispersion                                                Ia       Ib         Ic                                             ______________________________________                                        Binder from Ex-                                                                            937.5      937.5      937.5                                      ample 1                                                                       Crosslinking agents                                                           from Examples 2-4                                                             Crosslinking agent I                                                                       528.0      --         --                                         Crosslinking agent II                                                                      --         528.0      --                                         Crosslinking agent III                                                                     --         --         388.2                                      Dibutyl-tin dilaurate                                                                      8.0        --         --                                         Lead-II octoate                                                                            --         28.0       28.0                                       solution (24% of Pb)                                                          Antifoam solution                                                                          1.2        1.2        1.2                                        Glacial acetic acid                                                                        23.0       23.0       23.0                                       Deionized water 1                                                                          751.5      751.5      891.3                                      Deionized water 2                                                                          960.0      960.0      960.0                                      Solids content (60                                                                         34.2%      35.1%      34.4%                                      minutes, 130° C.)                                                      ______________________________________                                    

PREPARATION OF BINDER II AND DISPERSION II

1175 parts of a commercially available epoxide resin based on bisphenolA (epoxide equivalent weight EEW=188), 325 parts of 2-ethylhexanol and75 parts of xylene are introduced into a suitable reactor and heated to125° C. 7 parts of dimethylbenzylamine are then added and thetemperature is kept at 138° C., until an EEW of 1125 has been reached.1155 parts of crosslinking agent I are then added. As a result, thetemperature falls to 90° C. 94 parts of a reaction product of 1 mole ofdiethylenetriamine with 2 moles of methyl isobutyl ketone (MIBK), 70% inMIBK, and 75 parts of methylethanolamine are added. As a result, thetemperature rises again. It is maintained for 1 hour at 115° C., and 123parts of propylene glycol monophenyl ether and 60 parts of lead octoateare then mixed in. The resin is dispersed in 3861 parts of deionizedwater to which 26 parts of glacial acetic acid and 24 parts of acommercially available emulsifier solution has been added beforehand.The solids content of the dispersion is 35%.

PREPARATION OF BINDERS III AND IV AND OF DISPERSIONS III AND IV

The procedure followed is as in the preparation of binder II anddispersion II. The changed weights taken are as follows:

    ______________________________________                                                       Example III                                                                              Example IV                                          ______________________________________                                        Epoxide resin (EEW = 188)                                                                      1225         1172                                            Cyclohexanol     245          --                                              Phenylglycol     --           322                                             Xylene           --           75                                              MIBK             73           --                                              Dimethylbenzylamine                                                                             7            7                                              Crosslinking agent (according                                                                   1155 (II)     1150 (III)                                    to Example)*                                                                  Diethanolamine   171          82                                              Methylethanolamine                                                                             --           58                                              Hexylglycol      165          122                                             Lead octoate     68           60                                              Deionized water  3808         3877                                            Glacial acetic acid                                                                            59           51                                              Emulsifier solution                                                                            24           24                                              ______________________________________                                         *The crosslinking agent is not added as in Example II when the EEW limit      is reached (for Example III: EEW = 875, for Example IV: EEW = 930), but       after the hexylglycol has been mixed in.                                      For this purpose, the resin solution is cooled to 95° C.          

PREPARATION OF BINDER V

1098 parts of a commercially available epoxide resin based on bisphenolA (epoxide equivalent weight EEW=188), 322 parts of phenylglycol and 71parts of xylene are introduced into a suitable reaction vessel andheated to 133° C. As soon as the temperature has reached 125° C., 7parts of dimethylbenzylamine are added, and the temperature is allowedto rise further and is then maintained at 133° C., until an EEW of 1170has been reached. The mixture is rapidly cooled to 90°, and 337 parts ofthe amine salt solution are added. As a result, the temperature fallseven further. It is maintained at 80° C., until the acid number is <1.1162 parts of crosslinking agent IV, 65 parts of lead octoate and 165parts of hexylglycol are then added. This resin solution is thendispersed in 3773 parts of deionized water. The solids content of thedispersion is 35%.

    ______________________________________                                        Preparation of binder VI                                                      The procedure is as in the preparation of binder                              dispersion V, but the following components were used.                         ______________________________________                                        Epoxide resin (EEW 188) 1077   parts                                          Hexylglycol             314    parts                                          Methyl isobutyl ketone  90     parts                                          Dimethylbenzylamine     7      parts                                          Stopped at EEW = 930                                                          Amine salt solution     392    parts                                          Crosslinking agent I    1157   parts                                          Propylene glycol monophenyl ether                                                                     135    parts                                          Deionized water         3828   parts                                          ______________________________________                                    

PREPARATION OF BINDER VII

A reactor fitted with a heating device, a stirrer, a cooler, athermometer and a nitrogen inlet is charged with 1053 parts of abisphenol A epoxide resin having an epoxide equivalent weight of 188,205 parts of hexylglycol, 20 parts of xylene and 5 parts ofdimethylbenzylamine. The temperature is raised to 131° C. and thereaction is continued until an epoxide equivalent weight of 440 has beenreached. 376 parts of a commercially available polycaprolactone-diol ofmolecular weight 535 and a further 2 parts of dimethylbenzylamine arethen added. The reaction is continued at 131° C., until the reactionmixture has an epoxide equivalent weight of 1100. 1260 parts ofcrosslinking agent I are then added. The reaction temperature is loweredto 90° C. by external cooling. 110 parts of a reaction product of 1 moleof diethylenetriamine and 2 moles of methyl isobutyl ketone (70% inmethyl isobutyl ketone) and 83 parts of N-methylethanolamine are thenadded to the reaction mixture, the temperature rising exothermally to115° C. The temperature is then held at 110° C. for 1 further hour.Subsequently, the reaction batch is diluted with 134 parts of propyleneglycol phenol ether, cooled to 95° C. and discharged. This gives a clearresin solution.

Meanwhile, a dispersing bath is prepared from 1472 parts of deionizedwater, 23 parts of glacial acetic acid and 1 part of a commerciallyavailable antifoam, and 1800 parts of the resin solution described aboveare introduced into this bath. The dispersion mixture is stirred for afurther 2 hours, before dilution with a further 942 parts of deionizedwater. This gives a low-viscosity dispersion having a solids content of35%.

    ______________________________________                                         Preparation of binder VIII                                                   ______________________________________                                        Epoxide resin having an EEW of 188                                                                     978    parts                                         2-Ethylhexanol           109    parts                                         Xylene                   19     parts                                         Dimethylbenzylamine      5      parts                                         Polycaprolactone-diol MW = 535                                                                         349    parts                                         Dimethylbenzylamine      2      parts                                         Crosslinking agent I     1156   parts                                         Diethylenetriamine ketimine                                                                            102    parts                                         according to Example 1                                                        N--Methylethanolamine    77     parts                                         Propylene glycol phenol ether                                                                          122    parts                                         Resin solution           1800   parts                                         Deionized water          1472   parts                                         Glacial acetic acid      24     parts                                         Antifoam                 1      part                                          Deionized water          942    parts                                         ______________________________________                                    

The procedure is analogous to the Example of the preparation of binderVII, but in this case 2-ethylhexanol is used as the monoalcohol. Thisgives an aqueous dispersion having a solids content of 35%.

PREPARATION OF BINDER IX

718 parts of a commercially available epoxide resin based on bisphenol A(epoxide equivalent weight EEW 188), 132 parts of phenylglycol and 51parts of xylene are introduced into a suitable reactor and heated to130° C. 5 parts of dimethylbenzylamine are then added. After theexothermic reaction has subsided, the temperature is maintained at 137°C., until an EEW of 425 has been reached, and 287 parts of a dimer fattyacid (Pripol 1022 from Unichema) and 3 parts of dimethylbenzylamine arethen added and the reaction is continued at 130° C., until an EEW of1130 has been reached. The mixture is then cooled to 90° C.

36 parts of methylethanolamine and 50 parts of diethanolamine are thenadded. Due to the exothermic reaction, the temperature rises and ismaintained for 1 hour at 115° C. 750 parts of crosslinking agent IV, 118parts of hexylglycol and 43 parts of lead octoate are then added andmixed in for 30 minutes at 90° C. The resin solution is then dispersedin 2760 parts of deionized water, 18 parts of an emulsifier solution and29 parts of glacial acetic acid. The solids content of the dispersion is35%.

PREPARATION OF BINDER X

703 parts of a commercially available epoxide resin based on bisphenol A(epoxide equivalent weight--EEW--188), 133 parts of 3-cyclohexylpropanoland 42 parts of xylene are introduced into a suitable reactor. Thereaction batch is heated to 130° C., and 4 parts of dimethylbenzylamineare added. After the exothermic reaction has subsided, the batch ismaintained at 137° C., until an EEW of 430 has been reached. 291 partsof a reaction product of 1 mole of hexamethylenediamine and 2 moles ofCardura E 10 (EEW 254) are then added. The batch is then maintained at130° C., until an EEW of 1150 has been reached, and is then rapidlycooled to 90° C.

98 parts of diethanolamine are then added. During this addition, thetemperature rises again and is maintained at 115° C. for 1 hour. 750parts of crosslinking agent IV, 121 parts of phenylglycol and 60 partsof lead octoate are then added and mixed in at 90° C. for 30 minutes.The resin solution is then dispersed into 2813 parts of deionized water,17 parts of an emulsifier solution and 28 parts of glacial acetic acid.The solids content is 35%.

PREPARATION OF BINDERS XI TO XIII

The epoxide resin (based on bisphenol A, epoxide equivalent weightEEW=188) together with the monoalcohol and xylene is introduced into asuitable reactor, and the mixture is heated to 125° C.Dimethylbenzylamine is then added, and a temperature of 135° C. ismaintained, until the EEW of the 1st stage has been reached. Theelasticized diphenol is then added, and the reaction is continued at135° C., until the 2nd EEW stage has been reached. The crosslinkingagent is then added, causing the temperature to fall to 90° C. Theamines are then mixed in. As a result, the temperature rises and ismaintained for 1 hour at 110° C. Hexylglycol and, if appropriate, leadoctoate are then added. The resin solution is dispersed in deionizedwater, to which glacial acetic acid and a commercially availableemulsifier mixture have been added beforehand.

The amounts used are listed in the table which follows.

Amounts used for preparation of the binders

    ______________________________________                                        Binder dispersion                                                                           XI         XII       XIII                                       ______________________________________                                        Epoxide resin 870        860       909                                        Hexylglycol   169        --        --                                         2-Ethylhexanol                                                                              --         149       --                                         Phenylglycol  --         --        167                                        Xylene         51         50        54                                        Dimethylbenzylamine                                                                          5          5         5                                         Diphenol/type  446/I       510/II    457/III                                  Ketimine      124        --        --                                         Methylethanolamine                                                                           69        --         45                                        Diethanolamine                                                                              --         120        64                                        Crosslinking agent/type                                                                      1155/I      1155/II 1155/III                                   Hexylglycol   159        147       122                                        Lead octoate  --          73        61                                        Deionized water                                                                             3894       3863      3897                                       Glacial acetic acid                                                                          34         41        40                                        Emulsifier solution                                                                          24         25        24                                        EEW 1st stage 430        430       430                                        EEW 2nd stage 1225       1250      1200                                       ______________________________________                                    

PREPARATION OF BINDER DISPERSION XIV

1116 parts of a commercially available epoxide resin based on bisphenolA (epoxide equivalent weight EEW=188), 325 parts of2,2,4-trimethylpentane-1,3-diol and 87 parts of xylene are introducedinto a suitable reactor and heated to 125° C. 7 parts ofdimethylbenzylamine are added, and the temperature is allowed to rise to137° C. This temperature is maintained until an EEW of 940 has beenreached. 1155 parts of crosslinking agent I are then added, causing thetemperature to fall to 95° C. 160 parts of a reaction product of 1 moleof diethylenetriamine and 2 moles of methyl isobutyl ketone (MIBK), 70%in MIBK, and 89 parts of methylethanolamine are then added. As a result,the temperature rises and is maintained for 1 hour at 110° C. 171 partsof hexylglycol are then added and mixed in for 15 minutes. The resinsolution is then dispersed in 3829 parts of deionized water, 36 parts ofglacial acetic acid and 25 parts of an emulsifier solution. The solidscontent of the dispersion is about 35%.

PREPARATION OF BINDER DISPERSIONS XV TO XVII

The epoxide resin, the diol and the xylene are introduced into asuitable reactor. This mixture is heated to 125° C., anddimethylbenzylamine is added. The reaction is then continued at 135° C.,until the EEW of the first stage has been reached. The elasticizingcomponent and, if appropriate, further dimethylbenzylamine are thenadded. The reaction is continued until the EEW of the second stage hasbeen reached. The amines are then added, and the temperature ismaintained for 1 hour at 115° C. Subsequently, hexylglycol, lead octoateand crosslinking agent are added, and these are mixed in at 85° C. Theresin solution is then dispersed in deionized water to which glacialacetic acid and an emulsifier solution have been added. The particularweights used are listed in the table which follows.

    ______________________________________                                        Dispersion       XV        XVI     XVII                                       ______________________________________                                        Epoxide resin    970       937     942                                        2,2,4-Trimethylpentane-1,3-diol                                                                188       --      --                                         2-Methylpropane-1,2-diol                                                                       --        112     113                                        Xylene            69       52      53                                         Dimethylbenzylamine                                                                             6         5       5                                         EEW 1st stage    430       405     405                                        Polycaprolactone-diol                                                                          348       --      --                                         Dimethylbenzylamine                                                                             4        --      --                                         Polyphenol I     --        481     --                                         Polyphenol II    --        --      474                                        EEW 2nd stage    1130      1170    1170                                       Methylethanolamine                                                                             --        47      47                                         Diethanolamine   135       65      66                                         Crosslinking agent II                                                                          1155      1155    1155                                       Hexylglycol      147       159     123                                        Lead octoate      61       61      61                                         Deionized water  3843      3857    3888                                       Glacial acetic acid                                                                             50       45      49                                         Emulsifier solution                                                                             24       24      24                                         ______________________________________                                    

PREPARATION OF BINDER I FOR A GRINDING RESIN

800 parts of butylglycol are added to 953 parts of a commerciallyavailable epoxide resin based on bisphenol A and having an epoxideequivalent weight of 890. The mixture is heated to 80° C. 221 parts of areaction product of 101 parts of diethanolamine and 120 parts of 80%aqueous lactic acid are then added to the resin solution. The reactionis carried out at 80° C., until the acid number has fallen to less than1.

PREPARATION OF BINDER II FOR A GRINDING RESIN

1092 parts of a commercially available epoxide resin based on bisphenolA (epoxide equivalent weight EEW=188), 283 parts of 2-ethylhexanol and69 parts of methyl isobutyl ketone are introduced into a suitablereaction vessel and heated to 135° C. 6 parts of dimethylbenzylamine areadded to 125° C. The temperature is maintained at 135° C., until an EEWof 910 has been reached. 467 parts of the semi-masked isocyanate arethen added and the batch is maintained at 125° C. for 1 hour. 677 partsof butyl glycol are then added. As a result, the batch cools. Thetemperature is adjusted to 80° C., and 441 parts of the amine saltsolution are added. The temperature is maintained at 80° C., until theacid number is <1. The resin solution is then adjusted to a solidscontent of 60% by means of 465 parts of butylglycol.

PREPARATION OF BINDER III FOR A GRINDING RESIN

The procedure is as in the preparation of binder 3. However, after anEEW of 1150 has been reached, semi-masked isocyanate is not added and,instead, the mixture is immediately cooled to 80° C. and the firstquantity of butylglycol is added. The following components are used.

    ______________________________________                                        Epoxide resin (EEW = 188)                                                                            1393   parts                                           2-Ethylhexanol         385    parts                                           Methyl isobutyl ketone 89     parts                                           Dimethylbenzylamine    7      parts                                           Butylglycol            861    parts                                           Sulfide/acid salt mixture                                                                            474    parts                                           Butylglycol            291    parts                                           ______________________________________                                    

PREPARATION OF BINDER IV FOR A GRINDING RESIN

1426 parts of a commercially available epoxide resin based on bisphenolA (epoxide equivalent weight EEW=188), 277 parts of2,2,4-trimethylpentane-1,3-diol and 85 parts of methyl isobutyl ketoneare introduced into a suitable reaction vessel and heated to 132° C. Assoon as 125° C. have been reached, 9 parts of dimethylbenzylamine areadded. The temperature is then maintained at 132° C. until an EEW of 430has been reached. 718 parts of polyphenol II are then added. Thetemperature is maintained at 132° C., until an EEW of 1240 has beenreached. The mixture is then rapidly cooled to 90° C., and 288 parts ofthe semi-masked isocyanate are added. The temperature is maintained at90° C. for 2 hours, and 1067 parts of butylglycol and 547 parts of theamine salt solution are then mixed in. The temperature is maintained at80° C., until the acid number is <1. The solids content of the resinsolution is then adjusted to 60% by means of 583 parts of butylglycol.

PREPARATION OF A GRAY PIGMENT PASTE (I)

1800 parts of the grinding resin I and 2447 parts of deionized water aretaken and blended with 2460 parts of TiO₂, 590 parts of an extenderbased on aluminum silicate, 135 parts of lead silicate and 37 parts ofcarbon black. This mixture is comminuted in a grinding apparatus to aHegman fineness of 5 to 7. 1255 parts of deionized water are then addedin order to obtain the desired paste consistency. This gray paste isvery stable on storage.

PREPARATION OF A GRAY PIGMENT PASTE (II)

1800 parts of grinding resin II and 2447 parts of deionized water aretaken and blended with 2460 parts of TiO₂, 590 parts of an extenderbased on aluminum silicate, 135 parts of lead silicate and 37 parts ofcarbon black. This mixture is comminuted in a grinding apparatus to aHegman fineness of 5 to 7. 1255 parts of deionized water are then addedin order to obtain the desired paste consistency.

PREPARATION OF A GRAY PIGMENT PASTE (III)

1800 parts of binder V and 2447 parts of deionized water are taken andblended with 2460 parts of TiO₂, 590 parts of an extender based onaluminum silicate, 13 parts of lead silicate and 37 parts of carbonblack. This mixture is comminuted in a grinding apparatus a Hegmanfineness of 5 to 7. 1255 parts of deionized water are then added inorder to obtain the desired paste consistency.

PREPARATION OF A WHITE PIGMENT PASTE

1295 parts of grinding resin III are blended with 3170 parts of TiO₂, 30parts of a cationic surfactant and 210 parts of butylglycol. Thismixture is ground in a grinding apparatus to a Hegman fineness of lessthan 7. 210 parts of butylglycol are then added in order to adjust tothe desired paste consistency.

PREPARATION OF ELECTROCOATING BATHS I TO IV AND DEPOSITION OF COATINGFILMS

2000 parts by weight of the binder dispersions described above are ineach case mixed with 775 parts by weight of the gray pigment paste. Thesolids content of the bath is adjusted to 20% (150° C., 30 minutes) withdeionized water. The bath is then allowed to age for 3 days, withstirring. The coating films are deposited within 2 minutes onzinc-phosphatized sheet metal. The bath temperature during deposition is27° C. The deposited films are baked for 20 minutes at 180° C.

    __________________________________________________________________________    Deposition results                                                            Bath          Ia   Ib  Ic   II  III  IV                                       __________________________________________________________________________    Layer thickness (μm)                                                                     27/320                                                                             31/340                                                                            28/320                                                                             37/340                                                                            32/320                                                                             34/320                                   at voltage (V)                                                                Throwing power (cm)                                                                         20.5/360                                                                           21/360                                                                            20.5/380                                                                           21/360                                                                            22.5/360                                                                           21/380                                   at voltage                                                                    Flow*         1    0.5 0.5  0.5 0.5  0                                        Crater rating*                                                                              0.5  1   0.5  1   0    0                                        Erichsen cupping test (mm)                                                                  7.0  9.0 9.5  8.0 9.5  9.0                                      Cross cut*    0    0   0    0   0    0                                        __________________________________________________________________________     *0 = best rating, 5 = poorest rating                                     

PREPARATION OF ELECTROCOATING BATHS V-VIII AND DEPOSITION OF COATINGFILMS

2000 parts by weight of the binders V and VI described above are in eachcase mixed with 775 parts of the gray (II) or white pigment paste,respectively. The solids content of the bath is adjusted to 22% (150°C., 30 minutes) with deionized water. The baths are allowed to age for 3days, with stirring. The baths were prepared from the followingcomponents.

    ______________________________________                                                 Binder                                                                              Binder    White   Gray (II)                                             V     VI        paste   paste                                        ______________________________________                                        Bath V     x       --        --     x                                         Bath VI    x       --        x     --                                         Bath VII   --      x         --    x                                          Bath VIII  --      x         x     --                                         ______________________________________                                    

The coating films are deposited within 2 minutes on zinc-phosphatizedsheet metal. During the deposition, the bath temperature is 27° C. Thedeposited films are baked for 20 minutes at 180° C.

APPLICATION DATA AND TESTING OF THE COATINGS

    ______________________________________                                                        Bath  Bath    Bath    Bath                                                    V     VI      VII     VIII                                    ______________________________________                                        Layer thickness at 320 V (μm)                                                                30      32      27    33                                    Throwing power* at 340 V (cm)                                                                   20.8    19.7    21.5  20.1                                  Erichsen cupping test (mm)                                                                      9       7.3     8.7   7.6                                   Cross cut**       0       0.5     0     0.5                                   Flow**            0.5     1       0.5   0.5                                   Cratering tendency**                                                                            0       0.5     0     0                                     ______________________________________                                         *according to Ford                                                            **0 = best rating, 5 = poorest rating                                    

PREPARATION OF ELECTROCOATING BATHS IX TO XII AND DEPOSITION OF COATINGFILMS

2000 parts by weight of the binder dispersions VII to X described aboveare in each case mixed with 775 parts by weight of the gray pigmentpaste I. The solids content of the bath is adjusted to 20% (150° C., 30minutes) with deionized water. The bath is then allowed to age for 3days, with stirring. The coating films are deposited within 2 minutes onzinc-phosphatized sheet metal. During the deposition, the bathtemperature is 27° C. The deposited film are baked for 20 minutes at180° C.

DEPOSITION RESULTS

    ______________________________________                                        Bath             IX     X        XI   XII                                     Binder           VII    VIII     IX   X                                       Layer thickness (μm/V)                                                                      35     34       28   31                                      Throwing power (cm)                                                                            19.1   19.5     21.7 19.3                                    Surface*         1      1        0.5  1                                       Cratering*       0      0.5      0    1                                       ______________________________________                                         *0 = best rating, 5 = poorest rating                                     

PREPARATION OF ELECTROCOATING BATHS XIII TO XV AND DEPOSITION OF COATINGFILMS

The procedure is as in the preparation and deposition of baths IX toXII.

DEPOSITION RESULTS

    ______________________________________                                        Bath         XIII        XIV     XV                                           Layer thickness at                                                                         37/310      34/340  32/310                                       voltage (μm/V)                                                             Throwing power                                                                             19.5/320    21/370  20.5/350                                     at voltage (cm/V)                                                             Flow*        0.5         1       0.5                                          Cratering*   0           0       0.5                                          Erichsen cupping                                                                           7.5         9.0     9.5                                          test (mm)                                                                     ______________________________________                                    

PREPARATION OF ELECTROCOATING BATHS XVI TO XIX AND DEPOSITION OF COATINGFILMS

The procedure is as in the preparation and deposition of baths IX toXII.

DEPOSITION RESULTS

    ______________________________________                                        Bath            XVI    XVII    XVIII  XIX                                     Binder dispersion                                                                             XIV    XV      XVI    XVII                                    Layer thickness (μm)                                                                       48     51      45     44                                      at 360 V                                                                      Throwing power (cm)                                                                           19.8   20.7    21.5   20.3                                    at 360 V                                                                      Flow*            0.5   1        0.5   0                                       Cratering*      0      0       0      0                                       Erichsen cupping test (mm)                                                                    7       8.5    >10    >10                                     ______________________________________                                         *0 = best rating, 5 = poorest rating                                     

PREPARATION OF ELECTROCOATING BATHS XX AND XXI AND DEPOSITION OF COATINGFILMS

The procedure is as in the preparation and deposition of baths IX toXII, but the gray pigment paste (III) is used.

DEPOSITION RESULTS

    ______________________________________                                        Bath                  XX     XXI                                              Binder                XIV    XV                                               Layer thickness at 320 V (μm)                                                                    34     36                                               Throwing power* at 350 V (cm)                                                                       20.4   19.7                                             Erichsen cupping test (mm)                                                                          8.7    >10                                              Cross cut**           0      0                                                Flow**                0.5    0                                                Cratering tendency**  0      0                                                ______________________________________                                         *according to Ford                                                            **0 = best rating, 5 = poorest rating                                    

PREPARATION OF A FILLED MOLDING COMPOSITION@

3013 parts of a commercially available epoxide resin based onperhydrogenated bisphenol A (epoxide equivalent weight 240=EEW 240)together with 612 parts of 2-ethylhexanol are introduced into a suitablereactor and heated to 125° C. 17 parts of dimethylbenzylamine are thenadded and, after the exothermic reaction, the temperature is maintainedat 140° C., until an EEW of 1050 has been reached. The mixture is thencooled rapidly to 70° C., and 358 parts of glutaric anhydride are added.

This mixture is then mixed with 40% by weight, based on the resin/curingagent mixture, of powdered mica and homogenized in a kneader. Meanwhile,a suitable steel mold is prepared by spreading with a polyvinyl alcoholsolution (release coating). In this mold, plates of 3.5 mm thickness arecompression-molded at 180° C. The test plates thus produced have adielectric strength of >600 KV/cm and a tracking resistance KB (DIN53,480) of 450.

PREPARATION OF AN EPOXIDE RESIN ADHESIVE

2695 parts of a commercially available epoxide resin based on bisphenolA (epoxide equivalent weight EEW=177) and 788 parts of phenylglycol areintroduced into a suitable reactor and heated to 125° C. 17 parts ofdimethylbenzylamine are then added and the temperature is maintained at135° C., until an epoxide equivalent weight of 870 has been reached. Thebatch is then rapidly cooled.

To prepare the adhesive, 90 parts of the resin are mixed with 10 partsof Versamid 140 (commercial product from Schering AG, Bergkamen,polyamide-amine). This adhesive is suitable for the bonding of metals,even of moist metal components. The adhesive is applied to the areas tobe bonded, and these are fitted together and allowed to cure. Thetensile strength of the bond is 300 Kp/cm².

What is claimed is:
 1. A process for electrophoretically coating anelectrically conductive substrate, connected as the cathode, from anaqueous bath based on a cationic binder at least partially neutralizedwith acids, the binder being self-crosslinkable or being crosslinkabledue to the presence in said bath of a crosslinking agent, wherein thebinder is comprised of a synthetic resin prepared by reacting:A. adiepoxide, or a mixture of diepoxides, having an epoxide equivalentweight of less than about 500, with B. a compound with a hydroxyl group,which is reactive towards epoxide groups, wherein said hydroxyl groupcontaining compound and said diepoxide are in a molar ratio of about 2:1to about 7:6 and are reacted at temperatures from about 100° C. to about180° C. in an organic solvent free of hydroxyl groups, said syntheticresin having terminal epoxide groups and a mean molecular weight fromabout 400 to about
 5000. 2. The process according to claim 1 whereinsaid molar ratio is about 2:1 to about 5:4.
 3. The process according toclaim 1 wherein said molar ratio is about 2:1 to about 4:3.
 4. Theprocess according to claim 1 wherein said reaction is conducted in thepresence of a tertiary amine catalyst.